Recently, concern has been raised regarding the impact of a common class of pesticide known as neonicotinoids (pronounced neo-nih-CAH-tin-oids) on honey bees, (Apis mellifera, Figure 1) and native bee pollinators. Many people feel the decline in honey bee populations known as Colony Collapse Disorder (CCD) is directly linked to the increased use of these products.
In this paper, we will discuss the use of neonicotinoids as well as declines in honey bee populations. Finally, we will review what is currently known about the relationship between neonicotinoid pesticides and honey bees.
What are Neonicotinoids?
Neonicotinoids are systemic insecticides that are taken up by a plant through either its roots or leaves and move through the plant just like water and nutrients do. These insecticides provide very effective control of piercing and sucking insects. Over the last few years, the neonicotinoid class of insecticides has become important for use in agriculture and home landscapes. There are currently more than 465 products containing neonicotinoids (often called “neonics”) approved for use in the state of Washington. Approximately 150 are approved for use in the home or garden.
One of the main advantages for using neonicotinoid products is that they move systemically within the plant, thus reducing the direct pesticide exposure to both the applicator and the environment. Ironically, it is this systemic action that makes the neonicotinoids a problem for honey bees and other pollinators: because a neonicotinoid pesticide spreads within the entire plant, it can also be found in the nectar and pollen of the flowers.
In laboratory experiments, researchers have documented several neonicotinoid products that are toxic to bees. Depending on the amount of exposure to neonicotinoids, the effect on bees can be either sub-lethal or lethal. The sub-lethal effects of neonicotinoids include impaired learning behavior, short- and long-term memory loss, reduced fecundity (fertility and reproduction), and altered foraging behavior and motor activity of the bees. Researchers have documented similar issues with other pesticides including some products used by beekeepers to control Varroa, a parasitic mite of the honey bee. Neonicotinoids have also been implicated, along with some fungicides, in either depressing bees’ immune systems or increasing their susceptibility to biological infections (Wu et al., 2012; Pettis et al., 2013).
Exposure levels from dust created during planting of neonicotinoid-treated seed are known to have a devastating lethal impact on honey bees. However, this mode of exposure can be avoided and more work needs to be done on controlling levels of dust during planting. A more pressing concern is the chronic exposure of bees to neonicotinoids in nectar and pollen, as well as in water expressed from plants via a process known as guttation, that is picked up by foraging bees and brought back to the hive.
As is evident from the articles cited in Table 1, a great deal of research is currently under way, in both Europe and the United States, looking very intently at the effects of neonicotinoids on honey bees. Researchers at the University of Minnesota, Washington State University, and Washington Department of Agriculture are specifically looking at the issue of neonicotinoids in urban areas.